If you have a few double unders but you are not consistent, reduce the reps and only count your double unders.
If you have zero double udners and you really don't care to achieve them, do 50 single unders.
If you have zero but you DO want them, attempt them for 60 sec each round.

Toes to Bar - reduce reps if you cannot do unbroken for your first set.
Zero toes to bar? 5 stall bar skin the cats.